Gas used in industrial applications is provided in a variety of containers, which have a variety of characteristic pressures. Examples of such containers are high-pressure cylinders, liquid dewars, and bulk tanks. Additionally, different types of gas are stored at different characteristic pressures.
Gas supply manifolds allow one of two or more gas sources to supply gas to a common outlet. In one type of such a manifold, the selection of the gas source is performed by manually operating one or more valves to connect the desired gas source to the outlet. To prevent an interruption of the gas supply, an operator must be present and must switch to another gas source before the source in use is exhausted.
Some conventional gas supply manifolds provide an uninterrupted supply of gas by using a collection of pressure regulators and check valves to ensure that gas from only one source flows to the outlet. This type of manifold is described in U.S. Pat. No. 6,260,568 to Hsu, et al. When the gas source currently in use is depleted, the falling pressure from that source causes the regulators and valves to respond pneumatically to cut off the flow from the depleted source and to allow the gas from another source to begin flowing to the outlet. Such manifolds, however, must be reconfigured or manually adjusted when a new type of container is connected, or when used with a different type of gas.
Other conventional gas supply manifolds that provide an uninterrupted supply of gas use pressure sensors connected to electrically operated valves to change from one gas source to another, when the first source becomes exhausted. The pressure sensor is a pressure-operated electrical switch that closes or opens when the pressure is above or below a set level. Thus, when the source in use becomes depleted and its pressure falls below a set level, the associated pressure sensor closes, causing pre-selected valves to open and close to connect another gas source to the outlet. This type of manifold, too, must be reconfigured or manually adjusted when a new type of container is connected, or when used with a different type of gas.